The present invention relates to an electrochemical cell and, more particularly, to a primary electrochemical cell having a carbon cathode structure of improved design.
Primary electrochemical cells are utilized for a wide variety of applications and are commonly available in a large assortment of sizes and shapes. Furthermore, a number of electrochemical systems are known for incorporation into such primary electrochemical cells. Many of these electrochemical cells utilize a carbon cathode structure. By way of example, in U.S. Pat. No. 4,060,668, in the name of Franz Goebel and assigned to GTE Laboratories Incorporated, there is disclosed an electrochemical system including an anode, a carbon current collector cathode structure, and an electrolytic solution in contact with the anode and the carbon current collector cathode structure. The carbon current collector cathode structure employed in this electrochemical system includes a preformed porous cylindrical carbon structure of a specified length (as determined by the size of the cell), and a twisted metal cathode current collector impressed into and along the carbon structure. The porous carbon structure comprises an aggregation of a large number of porous semi-rigid globules which are pressed together in a manner to define a multiplicity of electrolyte channels. By virtue of these channels, the electrolytic solution can diffuse throughout the porous carbon structure and contact the cathodic particles of the structure.
While carbon current collector cathode structures as described hereinabove can be constructed and successfully employed within electrochemical cells, they nonetheless are subject to numerous possible problems and disadvantages. More particularly, the preformed porous carbon structures are inherently fragile and therefore difficult to produce in any reasonable or substantial length (e.g., 2 inches or more) without breaking or falling apart. Further, even when a carbon structure is successfully formed to the desired length, the subsequent act of impressing a metal cathode current collector into the preformed carbon structure, either by twisting or forcing the metal cathode current collector logitudinally into the preformed carbon structure, cannot be controlled with great accuracy. As a result, the mechanical and electrical contact between the twisted metal cathode current collector and the preformed carbon structure may be inadequate to satisfy the stringent requirements and specifications of the electrochemical cell in which such structure is to be used.